Treatment of artificial filaments, yarns, foils, films and the like containing organic derivatives of cellulose



Patented Mar. 29, 1938 UNITED STATES TREATIHENT OF ARTIFICIAL FILAMENTS, YARNS, FOILS, FILMS AND THE LIKE CON TAINING ORGANIC DERIVATIVES 0F GEL- LULOSE Henry Dreyfus, London, England No Drawing. Application March 28, 1936, derial No. 71,455. In Great Britain April 3, 1935 6 Claims.

This invention relates to improvements in the treatment of artificial filaments, yarns, foils, films and similar materials having a basis of cellulose acetate or other organic derivative of cellulose and particularly to improvements in processes for stretching such materials while they are softened by means of organic softening agents. This application is a continuation in part of my application S. No. 378,684 filed July 16, 1929.

It has now been discovered that improved results in the stretching of artificial filaments, yarns, foils, films and similar materials having a basis of organic derivatives of cellulose, particularly with respect to the tensile strength of the products and the smoothness or regularity with which the stretching takes place, may be obtained by softening the materials by means of a medium comprising both a neutral organic softening agent for the materials and an acidic softening agent for the materials, ,so that the softening medium as a whole is acidic.

According to the present invention, therefore, artificial filaments, threads, yarns, foils, films and similar materials having a basis of cellulose acetate or other organic derivative of cellulose are softened by means of an acidic medium comprising a neutral organic softening agent and an acidic softening agent and are stretched while in the softened condition.

Among neutral organic softening agents which may be employed are for example diacetone alcohol. acetone, dioxane, the'monoand di-ethers of olefine glycols and polyolefine glycols, e. g. the monoand di-methyl and monoand di-ethyl ethers of ethylene glycol and propylene glycol, and the mono-ethyl ether of di-ethylene glycol, the esters and ether-esters of olefine glycols and polyolefine glycols, e. g. glycol mono-acetate and methyl glycol mono-acetate, formaldehyde, acetaldehyde, mono-, diand tri-acetins, dichlorethylene, methylene chloride and the like. The softening medium may contain mixtures of such neutral softening agents in addition to the acidic softening agent. Acidic softening agents suitable for the purpose of this invention are, for example, softening agents which are lower aliphatic acids, e. g. formic acid, acetic acid and lactic acid. Mixtures of acidic softening agents may be employed. In general the neutral and acidic softening agents will be present in the softening medium in solution in a suitable diluent which is inert towards the materials treated. Preferably such diluent is water or a watermiscible liquid, e. g. an alcohol, though waterimmiscible liquids, e. g. benzene, toluene and other hydrocarbons, may be employed.

Preferably the softening medium employed contains a high proportion of neutral softening agent and a relatively low proportion of acidic softening agent. Thus the proportion of neutral softening agent may be 25-65%, and preferably 40-55%, of the softening medium and the proportion of acidic softening agent may be 2 or 5 up to about 19% of the softening medium. For ex ample, an aqueous softening medium containing 44-48% of dioxane and 2-5% of acetic acid may be employed.

The stretching operation may be applied to artificial filaments and other materials during the application ofthe softening medium thereto or it may be delayed until the full softening action of the medium on the materials is produced. Artificial filaments, threads and similar materials may be softened and stretched while they are in the form of hanks or other suitable packages. Preferably, however, the softening and stretching of both these materials and also of artificial films, foils and similar materials is carried out during the course of the travel of the materials from "one point to another, e. g. in the case of artificial filaments, threads and similar materials during their transfer from one bobbin to an-= other or during their travel from a spinning machine, or a cake or similar package, to a bobbin.

Preferably the softening medium is applied to the artificial materials by passing them through a bath of the medium. However, the medium may be applied by other methods as for example by passing the materials through a vessel containing the medium in the form of vapour under normal or super-atmospheric pressure, by spraying the materials with the medium, or by passing the materials in contact with rollers, wicks or other devices supplied with the medium, e. g. by spraying with the medium rollers over which the materials pass in travelling from one point to another.

The stretching operation may be efiectecl at normal atmospheric temperatures or at temperatures below or above atmospheric temperature. e. g. at 50 or 70 C., depending on the strength and nature of the softening medium applied to the materials and the degree of stretch which it is desired to effect. The stretching operation may be carried out in a single stage or in a plurality of stages and in the latter case the stages may follow directly after one another or, as described in U. S. application S. No. 573,424 filed 6th November 1931, rest" stages during which the materials are not stretched may be interposed between any two stages of stretching. In the stretching of artificial filaments, threads and similar materials the stretching may be applied to single filaments or threads or may be applied to a plurality of such filaments or threads simultaneously, e. g. to a plurality of filaments or threads arranged in warp formation, as described in U. S. application S. No. 602,844 filed 2nd April 1932. Artificial filaments, foils and like mateacid and 50% water.

rials may be stretched longitudinally and/or laterally or a longitudinal stretch may be combined with a lateral tension suflicient only to prevent lateral shrinkage of the foils due to the longitudinal tension. In this connection reference is made to U. S. applications S. Nos. 666,655 and 666,656 both filed 18th April 1933.

Artificial filaments, threads and similar materials may be stretched according to the present invention to a comparatively low degree, e. g. to -200% of their original length or to aconsiderably greater extent, e. g. to 400-600% of their original length or even more. In the case of artificial films, foils and similar materials lower degrees of stretch are in general more suitable.

The softening medium remaining in the materials after the stretching operation may, if sufficiently volatile, be removed by evaporation. The medium may also be removed by washing the materials with a. dilute alkaline medium in order to neutralize the acidic softening agent. Thus the materials may be washed with dilute solutions of sodium carbonate or ammonia. Advantageously the softening medium may be removed from the materials by washing them with washing media containing softening agents for the base of the materials in successively decreasing concentrations, then with dilute alkali and finally with water. In this way the lustre of the materials may be better preserved.

The materials stretched according to the present invention may be subjected to other aftertreatment processes, either prior or subsequent to the stretching operation, and such processes may be carried out either continuously with the stretching operation or separately therefrom. Thus, for example, artificial yarns may be stretched according to the present invention and then subjected to a shrinking operation, for example by passing them through a solution of methylene chloride in benzene, or to saponiflcation with an inorganic or organic base. Examples of suitable shrinking processes are given in U. .8. application S. No. 611,240 filed 13th May 1932 while U. S. applications S. Nos. 655,773 and 655,778 both filed 8th February 1933, 743,712 filed 12th September 1934, 752,376 filed 9th November 1934, 756,285 filedfith December 1934, and 326 filed 4th January 1935 describe suitable saponification processes.

The following example illustrates the invention but is not to be considered as limiting it in any way:-

Example A plurality of cellulose acetate threads are taken from a creel of bobbins and, by passage over guide rollers and through a reed, are arranged in warp formation, i. e. in the form of a sheet of substantially parallel threads. While in this formation the threads are passed round a feed roller, and thence through a bath of softening medium comprising 46% dioxane, 4% acetic The threads issuing from the bath are led round a draw roller and thence to suitable washing and drying apparatus and are finally rewound on bobbins. The draw roller is rotated so that its peripheral speed is three times as great as the peripheral speed of the feed roller, so'that between such rollers the materials are stretched to 300% of their original length.

The process of the present invention is of particular value in the stretching of artificial filaments, yarns, foils, films and similar materials containing cellulose acetate, but it may also be employed in the stretching of such materials containing other organic derivatives of cellulose, for example cellulose formate, cellulose propionate, cellulose butyrate, cellulose nitroacetate and other esters or mixed esters'of cellulose, cellulose ethers or mixed ethers, for example methyl, ethyl and benzyl cellulose, and cellulose etheresters, for example ethyl cellulose acetate and oxy-ethyl cellulose acetate.

Having described my invention what I desire to secure by Letters Patent is:- I

1. Process for the treatment of artificial filaments, threads, yarns, films, foils and similar materials having a basis cellulose which comprises softening such materials by treatment with an acidic softening medium comprising a' high proportion of a neutral organic softening agent and up to 10% of an organic acidic softening agent and subjecting the softened materials to a stretching operation.

2. Process for the treatment of artificial filaments, threads, yarns, films, foils and similar materials having a basis of cellulose acetate which comprises softening such materials by treatment with an acidic softening medium comprising a high proportion of a neutral organic softening agent and up to 10% of an organic acidic softening agent and subjecting the softened materials to a stretching operation.

3. Process for the treatment of artificial filaments, threads, yarns, films, foils and similar materials having a basis of organic derivatives of cellulose which comprises softening such materials by treatment with an acidic softening medium comprising 25 to 65% of a neutral organic softening agent and up to 10% of an organic acidic softening agent and softened materials to a stretching operation.

4. Process for the treatment of artificial filaments, threads, yarns, films, foils and similar materials having a basis of cellulose acetate which comprises softening such materials by treatment with an acidic softening medium comprising 40 to 55% of a neutral organic softening agent and 2 to 5% of an organic acidic softening agent and subjecting the softened materials to a stretching operation.

5. Process for the treatment of artificial filaments, threads, yarns, films, foils and similar materials having a basis of cellulose acetate which comprises softening such materials by treatment with anaqueous acidic softening medium comprising 25 to 65% of a neutral organic softening agent and 2 to 5% of an organic acidic softening agent and stretching the softened materials to more than 200% of their original length.

6. Process for the treatment of artificial filaments, threads, yarns, films, foils and similar materials having a basis of cellulose acetate which comprises softening such materials by treatment with an aqueous acidic softening medium comprising 40 to 55% of a neutral organic softening agent and 2 to 5% of an acidic softening agent selected from the group consisting of acetic acid, formic acid and lactic acid and stretching the softened materials to more than 200% of their original length.

HENRY DREYFUS.

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